An organic electroluminescence (EL) device is a promising solid-state emitting type inexpensive and large full-color display device, and has been extensively developed. In general, an organic EL device includes an emitting layer and a pair of opposing electrodes holding the emitting layer therebetween. When an electric field is applied between the electrodes, electrons are injected from the cathode and holes are injected from the anode. Further, the electrons recombine with the holes in the emitting layer to produce an excited state, and energy is emitted as light when the excited state returns to the ground state.
Conventional organic EL devices have a high driving voltage as compared with inorganic emitting diodes, and have a low luminance and a low luminous efficiency. Further, since their properties tend to deteriorate significantly, practical application thereof has not been realized yet. Although gradual improvements have been made on organic EL devices recently, further prolongation in life, improvement in luminous efficiency or the like are demanded.
The performance of an organic EL device has been gradually improved with improvements in emitting materials for an organic EL device. Improvement in luminous efficiency and prolongation in life of an organic EL device are important subjects leading to lowering in consumption in power and improvement of durability. Although improvement has been attained as a result of various studies, further improvement has been required.
As the emitting material of the emitting layer, a material which emits each color (red, green and blue, for example) has been developed. For example, a pyrene derivative is disclosed in Patent Documents 1 to 8 as a blue-emitting material.
However, there is a problem that the pyrene derivatives disclosed in Patent Documents 1 to 8 are not sufficient in respect of blue color purity and lifetime.